GaAs-on-Si solar cells for space use

The GaAs thin-film solar cells on Si substrates (GaAs-on-Si cells) are found to show higher end-of-life efficiency than the conventional GaAs cells fabricated on GaAs substrates (GaAs-on-GaAs cells) under high fluence 1 MeV electron irradiation of more than 1×10¹⁵ cm^-2. The first space flight of them has been carried out. 48 2 cm×2 cm GaAs-on-Si cells with an average AM0 total-area efficiency of 16.9% have been evaluated using the Engineering Test Satellite (ETS-VI). The GaAs-on-Si cells have been demonstrated to be more radiation-resistant in space than GaAs-on-GaAs cells and 50 μm thick Si cells. These results show that the GaAs-on-Si single-junction and InGaP/GaAs-on-Si multi-junction cells have great potential for space applications